Supine spinal magnetic resonance imaging with straightened lower extremities in spondylolisthesis: a comparison with the conventional technique

Diagnostic Performance of the Darth Vader Sign for the Diagnosis of Lumbar Spondylolysis in Routinely Acquired Abdominal CT

Spondylolysis is underdiagnosed and often missed in non-musculoskeletal abdominal CT imaging. Our aim was to assess the inter-reader agreement and diagnostic performance of a novel "Darth Vader sign" for the detection of spondylolysis in routine axial images. We performed a retrospective search in the institutional report archives through keyword strings for lumbar spondylolysis and spondylolisthesis. Abdominal CTs from 53 spondylolysis cases (41% female) and from controls (n = 6) without spine abnormalities were identified. A total of 139 single axial slices covering the lumbar spine (86 normal images, 40 with spondylolysis, 13 with degenerative spondylolisthesis without spondylolysis) were exported. Two radiology residents rated all images for the presence or absence of the "Darth Vader sign". The diagnostic accuracy for both readers, as well as the inter-reader agreement, was calculated. The "Darth Vader sign" showed an inter-reader agreement of 0.77. Using the "Darth Vader sign", spondylolysis was detected with a sensitivity and specificity of 65.0-88.2% and 96.2-99.0%, respectively. The "Darth Vader sign" shows excellent diagnostic performance at a substantial inter-reader agreement for the detection of spondylolysis. Using the "Darth Vader sign" in the CT reading routine may be an easy yet effective tool to improve the detection rate of spondylolysis in non-musculoskeletal cases and hence improve patient care.

Disc and nerve root findings on lumbar MRI with straightened v s flexed hips and knees-pilot study

OBJECTIVE:

To compare disc and nerve root findings, image quality, and pain between supine lumbar MRI positions with straightened v s flexed hips and knees.

METHODS:

In this prospective pilot study, 14 adults with sciatica or suspected lumbar radiculopathy underwent MRI supine with their hips and knees flexed and then straightened. For each position, two experienced radiologists assessed disc contour, location/size of disc herniation, nerve root affection, image quality, image evaluation difficulty, and sagittal angles between the vertebral bodies at each disc level L3-S1. Patients scored pain (0-10) after MRI in each position. We compared MRI assessments and mean pain scores (t-test, log-transformation) between the two positions.

RESULTS:

We found no clear difference in disc bulges, disc herniation, nerve root affection, image quality, or image evaluation difficulty between MRI with straightened v s flexed knees/hips. Herniation size differed ≤ 0.6 mm between the two positions. Sagittal angles between neighboring vertebral bodies differed ≤3.8°. Mean pain score after MRI with straightened v s flexed knees/hips was 4.64 v s 3.29 (p = 0.005).

CONCLUSION:

In this pilot study, supine lumbar MRI with straightened vs flexed hips/knees showed similar disc and nerve root findings. The straightened position appeared more painful.

ADVANCES IN KNOWLEDGE:

In previous studies, spondylolisthesis increased on supine MRI with straightened v s flexed lower limbs, but corresponding data on disc findings were lacking. In this pilot study, supine lumbar MRI with straightened rather than flexed hips and knees was more painful and did not improve the diagnosis of disc or nerve root findings.

Reliability of standing weight-bearing (0.25T) MR imaging findings and positional changes in the lumbar spine

OBJECTIVE

To test the reliability and absolute agreement of common degenerative findings in standing positional magnetic resonance imaging (pMRI).

METHODS AND MATERIALS

Low back pain patients with and without sciatica were consecutively enrolled to undergo a supine and standing pMRI. Three readers independently evaluated the standing pMRI for herniation, spinal stenosis, spondylolisthesis, HIZ lesions and facet joint effusion. The evaluation included a semi-quantitative grading of spinal stenosis, foraminal stenosis and spinal nerve root compression. The standing pMRI images were evaluated with full access to supine MRI. In case lower grades or the degenerative findings were not present in the supine images, this was reported separately as position-dependent changes. A subsample of 20 pMRI examinations was reevaluated after two months. The reproducibility was assessed by inter- and intra-reader reliability (kappa statistic) and absolute agreement between readers.

RESULTS

Fifty-six patients were included in this study. There was fair-to-substantial inter-reader reliability (κ 0.47 to 0.82) and high absolute agreement (72.3% to 99.1%) for the pMRI findings. The intra-reader assessment showed similar reliability and agreement (κ 0.36 to 0.85; absolute agreement: 62.5% to 98.8%). Positional changes between the supine and standing position showed a fair-to-moderate inter- and intra-reader reliability (κ 0.25 to 0.52; absolute agreement: 97.0% to 99.1).

CONCLUSION

Evaluation of the lumbar spine for degenerative findings by standing pMRI has acceptable reproducibility; however, positional changes from the supine to the standing position as an independent outcome should be interpreted with caution because of lower reliability, which calls for further standardisation.